FR2914028A1 - Hydraulic machine e.g. Francis turbine, for use in hydro-electricity production factory, has series of circular orifices constituting secondary water flow with abrasive particle content different from abrasive particle content of main flow - Google Patents

Abstract

The machine has a wheel supplied from a casing in which a forced conduit opens. A fixed guide vane series (6) and guiding vane series (7) guide a main flow (E1) that crosses the wheel, where the series (7) has lateral surfaces (71), which are wet by the flow. A circular orifices series (74) at a level of the surfaces (71) constitutes a secondary water flow (E2) with abrasive particle content different from abrasive particle content of the flow (E1). An independent claim is also included for a method for preventing wear out of a hydraulic machine.

Description

HYDRAULIC MACHINE AND METHOD OF PREVENTING THE WEAR OF SUCH

MACHINE

  The invention relates to a hydraulic machine and to a method for preventing wear of such a machine. For the purposes of the present invention, a hydraulic machine may be a turbine, a pump or a turbine-pump used, for example, in a hydro-electricity production plant. In the case of a turbine, the machine is installed on the water or fed with water from a tank into which flows one or more streams. Depending on the nature of the terrain they cross and weather conditions, rivers carry a variable amount of abrasive particles, such as sand or sediment. When these abrasive particles pass through the turbine, they wear the wet surfaces by the flow of water, resulting in expensive maintenance operations or even a risk of stopping the machine in case of undetected wear early. Similar problems occur with pumps and turbine pumps. It is these problems that the invention intends to remedy more particularly by proposing a new hydraulic machine structure in which the wear of a surface wetted by the main flow of water passing through the machine can be reduced or eliminated, which increases the life of the machine. To this end, the invention relates to a hydraulic machine traversed by a main flow of water and which comprises at least one member whose surface is wet. This machine is characterized in that it comprises means for injecting, at the level of the wetted surface, a secondary water flow with an abrasive particle content different from that of the main flow.

  Thanks to the invention, the fact of injecting at the level of the wetted surface, that is to say on this surface or in its immediate vicinity, a quantity of water whose abrasive particles content may be substantially lower that that of the main flow makes it possible to create, between this flow and the wetted surface, nets or a layer of water less loaded with abrasive particles than the main flow, these nets and this layer of water having less tendency to use the wet surface as the main flow. In other words, the means for injecting the secondary flow make it possible to isolate all or part of the wetted surface of the main flow, which can be heavily loaded with abrasive particles, for example after severe weather in the geographical areas crossed by the waterways feeding the machine. This is particularly the case during monsoon or glacial melt.

  According to advantageous but non-obligatory aspects of the invention, such a machine can incorporate one or more of the following characteristics: the injection means comprise means for reducing the abrasive particle content of a portion of a feed stream; water is the source of the main flow. - The injection means are connected to a different network of the supply circuit or discharge of the main flow. - The injection means comprise means for adjusting the flow and / or the pressure of the secondary flow. - The injection means comprise at least one thread flow passage constituting the secondary flow whose outlet is located on or in the vicinity of the wet surface. - The body that forms the wet surface is at least partially hollow and a partition of this body is provided with at least one water passage opening between the internal volume of the body and the wet surface. In this case, the member advantageously comprises a row of orifices extending in a direction generally perpendicular to the direction of advance, in the region where the openings open, the main water flow. - The body that forms the wet surface is full and provided with channels for supplying the secondary flow at this surface. According to a first embodiment of the invention, the member which forms the wetted surface is a director or a first director for guiding the flow of water towards a Francis turbine. According to another embodiment of the invention, the member is a turbine, pump or turbine-pump wheel. In this case, the turbine may be a Francis turbine whose blades are hollow, while the injection means comprise orifices in a side wall of at least one of its vanes and a supply duct which extends both in a fixed part of the turbine and in the ceiling or the belt of the wheel. According to a third embodiment of the invention, the member, a surface of which is wet, defines an annular space of entry of a portion of the main water flow in a labyrinth intended to form a landing. water, while the injection means are integrated in a fixed part of the machine and adapted to direct the secondary flow to a rotating part of the machine which carries the wet surface. According to a fourth embodiment of the invention, the member which carries the wetted surface is a water injector towards a turbine wheel, whereas the injection means are able to inject the quantity of water from the water. secondary flow on a peripheral surface of a needle of the injector and / or on a seat surface for this needle. The invention also relates to a method of preventing wear of a hydraulic machine as previously described and, more specifically, to a method which comprises a step of injecting, at the wetted surface of the machine, a secondary flow. of water with a different abrasive content than the main flow. Advantageously, the secondary flow, at the level of the wetted surface, is injected in sufficient quantity and in a suitable manner to create a layer of water with a content of abrasive particles different from that of the main flow, between the wetted surface. and this flow. It can further be provided that the method is implemented only when the abrasive particle content of the main flow exceeds a predetermined value, which is, for example, the case in the monsoon period. The invention will be better understood and other advantages thereof will emerge more clearly in the light of the following description of four embodiments of a hydraulic machine in accordance with its principle and a method for preventing the wear of such a machine, given purely by way of example and with reference to the accompanying drawings in which: - Figure 1 is a basic section of an energy production facility comprising a Francis turbine conforming to the invention; - Figure 2 is a partial section on a larger scale along the line II-II in Figure 1; - Figure 3 is a perspective view of a director shown in section in Figure 2; - Figure 4 is a view similar to Figure 3 for a director according to a second embodiment of the invention; - Figure 5 is a view similar to Figure 3 for a director according to a third embodiment of the invention; - Figure 6 is longitudinal section of a blade along the line VI-VI in Figure 1; FIG. 7 is a view on a larger scale of a labyrinth inlet slot of the turbine of FIG. 1; and FIG. 8 is a schematic representation of an injector used to control the injection of water into the buckets of a Pelton turbine according to the invention. The installation I shown in Figure 1 comprises a Francis turbine 1 whose wheel 2 is fed from a tank 3 into which a forced pipe 4 opens. The turbine 1 is coupled to an alternator 5 for generating electricity. The wheel 2 comprises blades 21 arranged between a ceiling 22 and a belt 23. Between the cover 3 and the wheel 2 are arranged a series of front-guides 6 and a series of guides 7 whose function is to guide a main flow. El which passes through the wheel 2 by licking the blades 21, which causes the rotation of the wheel 2 about a vertical axis ZZ. The front-guides 6 are fixed, whereas the guides 7 can pivot each around an axis Z7 parallel to the axis Z-Z ', in order to adjust the flow rate of the flow El.

  As can be seen in FIG. 2, the flow E1 licks off the lateral surfaces 61 of the front guides 6 and the lateral surfaces 71 of the guides 7. In this sense, these surfaces 61 and 71 are normally wetted by the flow El. this flow can be heavily loaded with abrasive particles, especially during periods of heavy rain or glacial melt in the geographical area crossed by the watercourse or streams supplying the pipe 4. In this case, the flow El can wear prematurely the surfaces 61 and 71. To limit this phenomenon of wear for the surfaces 71, the guides 7 are hollow and their respective internal volumes 72 are supplied with water having a relatively low abrasive particle content, starting from a circular pipe 8 around the axis ZZ 'itself fed by a system 9 called "water desalting" shown schematically in Figure 1. The grit removal system is used to eliminate a part of abrasive particles present in the water of the flow flowing in the pipe 4 and comprises a settling tank 91 in which is supplied at appropriate speed water carried by a nozzle 92 whose mouth is located in the pipe 4 or, according to variants not shown of the invention, in a feed tank of this pipe or in a downcomer located downstream of the turbine 1. The water supplied to the pipe 8 is therefore a portion of a water flow Fo constituting the source of the flow El. The water circulating in the quilting 92 can settle in the tank 91, so that the abrasive particles 93 fall on the bottom of the tank 91 and that the water is conveyed to the pipe 8 via a downstream pipe 94 has a lower abrasive particle content than the flow El. Of course, other grit removal systems, such as a hydrocyclone, can be used in the context of the invention .

  The pipe 8 is connected to the internal volume 72 of each director 7 by means of a pipe 82 extending in the fixed part of the turbine 1. There are provided as many pipes 82 as guide 7. Thus, the internal volume 72 each director 7 is fed from line 8 into water which will be described as "clear", that is to say which has a lower abrasive particle content than the flow El. sails or metal plates constituting the sides of the guides 7 and whose outer faces form the surfaces 71. Each plate 73 is pierced with a series of circular orifices 74 placing in communication the volume 72 and the surface 71. Thus, in operation of the installation I, the water coming from the pipe 8 can flow through the orifices 74 by forming threads F2, which constitutes, along the surfaces 71, a secondary flow E2 with a flow rate lower than that of the Thus, thanks to the invention, the urfaces 71 are wetted by both the flows E1 and E2. By a judicious choice of the position and the section of the orifices 74, the pressure and / or the flow rate of the clear water supply of the volume 72, the different threads F2 flowing on a surface 71 can meet, of such so that the flow E2 forms a continuous or quasi-continuous layer C2 of clear water which isolates all or part of the surface 71 of the flow El. This prevents the abrasive particles present in the flow E from coming into contact with or licking the surfaces 71. The orifices 74 are arranged on each plate 73 in a row which extends along a line DI or DI 'parallel to the axis Z7 and perpendicular to the direction of the flow E1 in the vicinity of the surface 71 corresponding. Thus, the streams of clear water leaving the orifices 74 are distributed over the surfaces 71 in the height of the flow El. As shown in FIG. 4, instead of a series of circular orifices 74, it is possible to use , a series of elongated slots 75 formed in the webs 73 being offset relative to each other along a longitudinal axis X7 of a director 7 in order to avoid mechanically weakening the webs 73 at these slots .

  The slots 75 are elongate in directions parallel to two straight lines DI and DI 'which are parallel to the axis Z7 and perpendicular to the flow E1 in the vicinity of the surfaces 71, which allows a distribution of the nets F2 of clear water in the height of the flow El. According to a not shown variant of the invention, the slots 75 may be elongated in directions parallel to the axis X7, in which case they are generally parallel to the flow El. The orifices 74 and the slots 74 are formed in the upstream portions of the surfaces 71, which allows the threads IF to cluster downstream of the orifices 74 or slits 75 on the surfaces 71 to form the secondary flow E2. As shown in FIG. 5, circular orifices 76 may be distributed in the webs 73, over most of the surfaces 71, which makes it possible to create nets of clear water F2 over most of these surfaces.

  As in the embodiment of FIG. 3, the clear water threads F2 belonging to the secondary flow E2 of the embodiments of FIGS. 4 and 5 tend to isolate the surfaces 71 with respect to the flow El which circulates around the director 7. As in the embodiment of FIG. 3, the threads F2 can meet to form a layer C2 of clear water which isolates all or part of the surfaces 71 with respect to the flow E1. variant of the invention which is not shown, the front-guides 6 can also be hollow and provided with orifices or slots for conveying streams of clear water on their outer surfaces 61. As particularly visible to FIG. 6, where the line 1-1 represents the section plane of FIG. 1 at a blade, the invention can also be implemented at the blades 21 of the wheel 2. The lateral surfaces are denoted 211 blades 21 and 212 their volume i a hollow interior defined between two webs 213 formed by welded metal plates in the vicinity of the leading edge 214 and the trailing edge 215 of each blade 21. Each web 213 is provided with a series of orifices 216 disposed at the vicinity of the leading edge 214, so that nets F2 clear water can flow from the volume 212 to and along the surfaces 211 when the volume 212 is supplied with clear water. To do this, a pipe 83 connects the pipe 8 to an annular space 84 located above the ceiling 22. This ceiling is pierced with openings 221 for feeding the interior volume 212 of each blade 21. Thus, the feed in clear water of the interior volume 212 of the blades 21 takes place by a duct which extends both in the fixed part of the turbine, as pipe 83, between the wheel 2 and the fixed part, in dry volume 84 , and in the wheel 2, as openings 221. Alternatively, instead of going through the ceiling 22, the supply duct of the volumetric 212 in clear water can pass through the belt 23. The orifices 216 are disposed in the upstream part of the surfaces 211 in a curved row which follows the geometry of the profile of each blade 21 and which is perpendicular to the flow E1 in the wheel 2.

  Thus, it is possible to create, by the sum of the threads F2 leaving the orifices 216, a secondary flow E2 relatively low in abrasive particles and which isolates the surfaces 211 of the main flow E1. According to non-represented variants of the invention, the holes 216 may not be arranged in the vicinity of the leading edge 214. They may, for example be grouped near the trailing edge 215, in an area close to the belt 23, even distributed over substantially an entire surface 211 or both, in a similar manner to what is envisaged for a director in Figure 5.

  In addition, the guides 7 and the blades may be only partially hollow. These bodies of the turbine 1 can even be solid, in which case they are provided with internal channels for feeding the flow E2 on the surfaces 71 and 211. Eo is noted the flow of water in the pipe 4. The flow Eo is the source of flows E1 and E2 and constitutes the total flow of water in the turbine 1. As can be seen from FIG. 7, the invention can also be used at a slot f delimited between a portion fixed 11 of the turbine and the wheel 2, this slot being intended to be traversed by a portion E3 of the flow E0 directed towards a labyrinth not shown, which forms, in a manner known per se, a water bearing. 231 is the surface of the belt 23 defining an edge of the slot f. Opposite the surface 231 and in the part 11 are defined several orifices 114 supplied with clear water from the pipe 8, this by means of pipes not shown. The orifices 114 make it possible to inject nets F2 of clear water towards the surface 231, which creates a secondary flow E2 and avoids that it is licked by the flow E3 which can contain abrasive particles in large proportions. Alternatively, in the case where the width of the slot f is chosen very small vis-à-vis the diameter of the wheel, it can, by itself constitute the labyrinth. In this case, depending on its flow, flow E2 can prevent flow E3 from taking place. In other words, only the flow E2 propagates in the slot f and the flow E0 is then equal to the sum of the flows E1 and E2. As can be seen from FIG. 8, the invention can also be implemented at the level of a water injector 10 towards the buckets of a Pelton turbine (not shown), this injector comprising a fixed body 101 as well as a needle 102 movable in translation along an axis X10 with respect to the body 101. The needle 102 is hollow and equipped with a row of orifices 104 supplied with clear water by a pipe 105 connected to a similar conduct line 8 of the first embodiment of FIG. production. This makes it possible to generate on the outer peripheral surface 103 of the needle 102 a secondary flow E2 formed of threads F2, this secondary flow tending to isolate the surface 103 of the main flow E, passing through the injector 10, which can be strongly loaded. in abrasive particles. The orifices 104 are arranged in an annular row, around the axis of advance of the needle 102, which is perpendicular to the main flow El in the injector 10. According to a variant of the invention which is not shown , in addition to or in place of the needle 102, the seat 106 of the injector 10 can also be equipped with a clear water injection means at its inner surface 107 facing the needle 103. According to another Alternatively, the needle 102 may be full. In this case, the pipe 105 divides into several supply ducts of the orifices 104. It is also possible to provide, inside the needle 102, an annular chamber for distributing the clear water coming from the pipe 105 between the pipes. orifices 104. The flow rate and / or the supply pressure of the orifices or distribution slots of the clear water on the wet surfaces 71 and the like, and consequently the flow rate and / or the pressure of the flow E2, can be adapted to the pressure or the flow rate of the flow El. To do this, it is possible to use a booster pump 95 installed on a duct 94 connecting the system 9 and the duct 8. Pumping pumps can, in Alternatively, be installed on the pipes 82 and 83. Alternatively, one can also use restrictions to control the flow and / or the pressure of the nets F2. According to a variant of the invention, instead of using a system 9 of grit removal or decantation of a portion of the water circulating or intended to flow in a pipe such as the pipe 4 or a feed pipe of the Injector 10 can be used as "clear water" water from an independent source, this water being less loaded abrasive particles than the main flow through the machine. For example, this water may be provided by a drinking water distribution network or drawn from the ground, so that its abrasive particle content does not depend on meteorological conditions. The implementation of the invention may be limited in time, especially for periods when the water constituting the main flow through the machine is heavily loaded with abrasive particles, such as monsoon or glacial melting periods. To this end, means for measuring the content of the flow El in abrasive particles may be provided in the installation I. The invention is not limited to the embodiments described and can be implemented in other hydraulic machine parts susceptible to be subjected to main flows having a relatively high abrasive particle content, for example at the level of the functional clearance provided between the guides 7 and the upper and lower flanges of the duct in which they are installed. The invention can be implemented at the buckets of a Pelton turbine or to protect any wet surface, including the water film seat surfaces, such as the upper surface of the ceiling of a Francis turbine wheel.

Claims (16)

  1. Hydraulic machine traversed by a main flow of water (El) and comprising at least one member (2; 7; 10) whose surface (71; 103; 211; 231) is wetted, characterized in that it comprises injection means (8, 9, 74, 76, 104, 114, 216), at the wetted surface, a secondary flow (E2) of water with an abrasive particle content different from that of the flow. principal (E1).   2. Machine according to claim 1, characterized in that the injection means (8, 74; 75; 76; 104; 114; 216) comprise means (9) for reducing the abrasive particle content of a portion. a flow (Eo) of water constituting the source of the main flow (El).   3. Machine according to claim 1, characterized in that the injection means (8, 74; 76; 104; 114; 216) are connected to a different network of the circuit (4) for supplying or discharging the fuel. main flow (El).   4. Machine according to one of the preceding claims, characterized in that the injection means (8, 9, 74; 75; 76; 104; 114; 216) comprise means (95) for adjusting the flow rate and / or pressure secondary flow (E2).   5. Machine according to one of the preceding claims, characterized in that the injection means comprise at least one passage (74; 76; 104; 114; 216) for the flow of threads (F2) constituting the secondary flow ( E2), the outlet of this passage being situated on or in the vicinity of the wetted surface (71; 103; 211).   6. Machine according to claim 5, characterized in that the member (7; 2; 10) is at least partially hollow and in that a partition of this member is provided with at least one orifice (74; 76; 104; 114; 216) of water passage between the internal volume (72; 212) of the member and the wetted surface (71; 103; 211).   7. Machine according to claim 6, characterized in that the member comprises a row of orifices (74; 75; 104; 216) extending in a direction (DI, D'1) generally perpendicular to the direction of advance in the region (71; 103; 211) where the openings open out of the main flow (E1).   8. Machine according to claim 5, characterized in that the member (7; 2; 10) is solid and provided with channels for supplying the secondary flow at the level of the wetted surface (71; 103; 211; 231). ).   9. Machine according to one of the preceding claims, characterized in that the member is a director (7) or a front-director (6) for guiding the main flow of water (E1) to a Francis turbine ( 1).   10. Machine according to one of claims 1 to 8, characterized in that the member is a wheel (2) turbine (1), pump or turbine pump.   11. Machine according to claim 10, characterized in that the turbine is a Francis turbine (1) whose blades (21) are hollow, in that the injection means comprise orifices (216) formed in a side wall ( 213) of at least one blade and a supply duct (83, 84, 221) extending both in a fixed part of the turbine and in the ceiling (22) or the belt (23) of the wheel .   12. Machine according to one of claims 1 to 8, characterized in that the member defines an annular space (f) input of a portion (E'1) of the main water flow (El) in a labyrinth for forming a water bearing and in that the injection means (114) are integrated with a fixed part (11) of the machine and able to direct the secondary flow (E2) towards a rotating part ( 2) of the machine that carries the wet surface (231).   13. Machine according to one of claims 1 to 8, characterized in that the member is an injector (10) of water to a turbine wheel and in that the injection means are capable of injecting the flow secondary (E2) on a peripheral surface (103) of a needle (102) of the injector and / or on a seat surface (107) (106) for the needle.   14. A method of preventing wear of a hydraulic machine (1) traversed by a main flow of water (El) comprising a member (2; 7; 10) having a surface (71; 103; 211; 231). is wet, characterized in that it comprises a step of injecting (F2), at the level of the wetted surface (71; 103; 211; 231), a secondary flow (E2) of water with different abrasive content from that of the main flow (El).   15. Process according to claim 14, characterized in that the secondary flow (E2) is injected at the level of the wetted surface (71; 103; 211; 231) in sufficient quantity (F2) and in a manner suitable for creating a layer of water (C2) with an abrasive particle content different from that of the main flow (El) between the wetted surface and this flow.   16. Method according to one of claims 14 or 15, characterized in that it is implemented only when the abrasive particles content of the main flow (El) exceeds a predetermined value.